The present invention relates to a system transferring carbon electrodes from a drying pallet onto a pitch impregnation pallet, which system has been developed for efficiently carrying out an improved invention of a cyclic operation of carbon electrode impregnation operating line.
Heretofore, in order to carrying out a vacuum pressure impregnation of pitch into carbon electrode, carbon electrodes are placed on a pallet, and put into a drying furnace, and after the heating and drying thereof, the electrodes are put into an impregnation tank, and after pumping out the air pumping out and degasing, molten pitch is poured therein and thereafter the electrodes are pressure impregnated with the pitch, and after the completion of the impregnation, they are rapidly cooled. However, in such method, there are drawbacks that when a palette having sticked pitch gets in the drying furnace, the pitch is heated at a high temperature and thereby become molten and flows down, with the result of contamination of the hot blast by pitch gas, deterioration of the working environment and an increase in public injury, causing fires of drying furnace and causing problems with the pallet transporting mechanism within the drying furnace. Also since the carbonization layer grows on the surface of the pallet, considerable time and effort are required for cleaning of the parts, resulting in a substantial decrease of the productivity.
By the technical progress made after development of this impregnation method, the impregnation procedures have been improved and at the present there is adopted a method in which a plurality of carbon electrodes are collectively loaded on a pallet having a specific shape and configuration and they are dipped in molten pitch in the loaded state. This impregnation operation is ordinarily conducted according to a process shown in the flow chart of FIG. 3. Referring to FIG. 3, a plurality of carbon electrodes are loaded on a pallet 8 (of which the shape and configuration are illustrated in FIGS. 1 and 2), and the pallet 8 is placed on transporting means 10 such as a conveyor and is first passed through a drying oven 11. In this drying oven 11, the carbon electrodes are pre-heated so that when the carbon electrodes are dipped in molten pitch in an impregnation vessel described hereinafter and while the voids in the carbon electrodes are impregnated with molten pitch, cooling and solidification of the impregnated pitch can be prevented. Accordingly, the drying oven 11 is disposed to pre-heat the carbon electrodes rather than to dry them.
The dried or pre-heated carbon electrodes 6 are brought down from the pallet 8 and shifted to another pallet 9, and the carbon electrodes 6 loaded on the pallet 9 are fed to an impregnation vessel 12 disposed on the same axial line X as that of the drying oven 11, where the carbon electrodes are impregnated with molten pitch. Then, the carbon electrodes 6 are passed through a cooling vessel 13 and brought down from the pallet. Thus, one cycle of the operation of impregnation of carbon electrodes is completed.
In the above illustrated process, it is apparently necessary to shift carbon electrodes loaded on the pallet 8 to another pallet 9. The reasons will now be described in detail.
The pallet 9 loading carbon electrodes thereon is dipped in molten pitch in the impregnation vessel 12 together with the carbon electrodes, and therefore, the pallet 9 is contaminated with pitch. If fresh carbon electrodes are loaded on such contaminated pallet 9 and they are passed through the drying oven 11, pitch which has adhered to the pallet 9 and been solidified thereon is molten and then gasified, while contaminating the drying oven 11 and its surrounding embodiment, and in some case, a fire is caused.
In order to avoid this disadvantage, it is necessary to use different pallets for passing carbon electrodes through the impregnation vessel 12 and for passing them through the drying oven, respectively, and it also is necessary to shift carbon electrodes from one pallet to another pallet.
Prior to passage through the impregnation vessel 12, carbon electrodes which have passed through the drying oven 11 are shifted from the pallet 8 used for passage through the drying oven 11 (hereinafter referred to as "drying pallet") to another pallet 9 to be used for passage through the impregnation vessel 12 (hereinafter referred to as "impregnating pallet"). In FIG. 1, the apparatus for performing this shifting operation is indicated by reference numeral 14.
Accordingly, a drying pallet and a pitch impregnation pallet are provided separately, and the carbon electrodes are transferred from one pallet to the other pallet in order to solve the drawbacks. However, as the method of transferring the carbon electrodes, there are many methods such as the use of a forklift etc., but after all, a full automatic system has.